A general object of the present disclosure is to provide a frame corner joint that is of light-weight rigid construction. Related objects of the present disclosure are to provide a corner key for making such a corner joint and a method of manufacturing such a corner joint.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
A frame corner joint in accordance with one aspect of the present disclosure includes first and second frame rails having hollow interiors of predetermined contours and ends in mitered abutment. A corner key has legs inserted into the mitered ends of the frame rails. End portions of the legs substantially fill the hollow interiors of the frame rails forming a substantially closed cavity within the frame rails and between the end portions of the corner key legs. Solidified resin foam is disposed within this cavity rigidifying the corner joint, while the remainder of the interiors of the frame rails preferably is substantially free of foam. At least one end portion of at least one leg of the corner key preferably has a flexible wall portion to permit escape of foam from within the cavity in the event of excess foam pressure. The hollow interiors of the frame rails preferably are mirror images of each other, and the legs of the corner key, including the end portions of the legs, preferably are mirror images of each other.
A corner key for joining mitered ends of frame rails to form a corner point, in accordance with another aspect of the disclosure, includes a one-piece body having mutually perpendicular legs. The legs are contoured to be secured by friction fit within the hollow interiors of the mitered rail ends and have end portions constructed substantially to fill the hollow rail interiors. At least one leg end portion, and preferably both of the leg end portions, preferably includes at least one flexible wall portion. The legs of the corner key, including the leg end portions, preferably are mirror images of each other.
A method of making a frame corner joint, in accordance with a further aspect of the present disclosure, includes providing first and second frame rails having hollow interiors of predetermined contours, and a corner key having legs with end portions constructed substantially to fill the hollow interiors of the frame rails. The frame rails are assembled over the corner key by inserting the legs into the hollow interiors of the frame rails until mitered ends of the frame rails abut each other, and the opposed end portions of the legs substantially fill the hollow interiors of the frame rails to form a substantially closed continuous cavity between the end portions of the corner key and the interiors of the frame rails. Resin foam is injected into the substantially closed cavity and allowed to cure to form a rigid corner joint. The step of injecting resin foam into the substantially closed cavity preferably is carried out by injecting the foam through aligned openings in at least one of the frame rails and at least one leg of the corner key.